Abstract

Medium range order in amorphous thin films of , a phase change memory material, was examined using electron nanodiffraction fluctuation electron microscopy. Variance measurements showed that medium range order existed at 0.36 and . The film was not at equilibrium and contained a few monoclinic nanocrystals with weak Bragg maxima at 0.33, 0.54, and , which are related to the equilibrium phase at this composition. We also determined the variance for amorphous silicon and amorphous silica and those results agree with others in the literature. It is expected that the medium range order is related to nucleation of the crystallization reaction in .

We thank Professor Paul Voyles, Department of Materials Science and Engineering, University of Wisconsin, Madison, for providing the programs for collecting and analyzing nanodiffraction patterns, Paul Perkes, ASU Leroy Eyring Center for Solid State Science, for assisting with programming, and Professor M. M. J. Treacy, ASU Department of Physics, for useful discussions. K.A.C. acknowledges funding from the Air Force Research Laboratory under Grant No. FA9559-07-1-0546.